Fix int32 type validation to reject decimal values (Closes #89)

.github/workflows/ci.yml

@@ -39,7 +39,7 @@ jobs:
                       for k in totals: totals[k]+=int(r.get(k,'0'))
                   except Exception:
                       pass
-          exp_tests=460
+          exp_tests=463
           exp_skipped=0
           if totals['tests']!=exp_tests or totals['skipped']!=exp_skipped:
               print(f"Unexpected test totals: {totals} != expected tests={exp_tests}, skipped={exp_skipped}")

json-java21-jtd/README.md

@@ -69,6 +69,14 @@ Validates primitive types:
 
 Supported types: `boolean`, `string`, `timestamp`, `int8`, `uint8`, `int16`, `uint16`, `int32`, `uint32`, `float32`, `float64`
 
+#### Integer Type Validation
+Integer types (`int8`, `uint8`, `int16`, `uint16`, `int32`, `uint32`) validate based on **numeric value**, not textual representation:
+
+- **Valid integers**: `3`, `3.0`, `3.000`, `42.00` (mathematically integers)
+- **Invalid integers**: `3.1`, `3.14`, `3.0001` (have fractional components)
+
+This follows RFC 8927 §2.2.3.1: "An integer value is a number without a fractional component."
+
 ### 4. Enum Schema
 Validates against string values:
 ```json

json-java21-jtd/src/main/java/json/java21/jtd/JtdSchema.java

@@ -244,6 +244,13 @@ Jtd.Result validateInteger(JsonValue instance, String type, boolean verboseError
           return Jtd.Result.failure(Jtd.Error.EXPECTED_INTEGER.message());
         }
 
+        // Handle BigDecimal - check if it has fractional component (not just scale > 0)
+        // RFC 8927 §2.2.3.1: "An integer value is a number without a fractional component"
+        // Values like 3.0 or 3.000 are valid integers despite positive scale, but 3.1 is not
+        if (value instanceof java.math.BigDecimal bd && bd.remainder(java.math.BigDecimal.ONE).signum() != 0) {
+          return Jtd.Result.failure(Jtd.Error.EXPECTED_INTEGER.message());
+        }
+
         // Convert to long for range checking
         long longValue = value.longValue();
 

json-java21-jtd/src/test/java/json/java21/jtd/TestRfc8927.java

@@ -2,6 +2,7 @@
 
 import jdk.sandbox.java.util.json.Json;
 import jdk.sandbox.java.util.json.JsonValue;
+import jdk.sandbox.java.util.json.JsonNumber;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -440,4 +441,93 @@ public void testRefSchemaRecursiveBad() throws Exception {
       .as("Recursive ref should reject heterogeneous nested data")
       .isFalse();
   }
+
+  /// Micro test to debug int32 validation with decimal values
+  /// Should reject non-integer values like 3.14 for int32 type
+  @Test
+  public void testInt32RejectsDecimal() throws Exception {
+    JsonValue schema = Json.parse("{\"type\": \"int32\"}");
+    JsonValue decimalValue = JsonNumber.of(new java.math.BigDecimal("3.14"));
+
+    LOG.info(() -> "Testing int32 validation against decimal value 3.14");
+    LOG.fine(() -> "Schema: " + schema);
+    LOG.fine(() -> "Instance: " + decimalValue);
+
+    Jtd validator = new Jtd();
+    Jtd.Result result = validator.validate(schema, decimalValue);
+
+    LOG.fine(() -> "Validation result: " + (result.isValid() ? "VALID" : "INVALID"));
+    if (!result.isValid()) {
+      LOG.fine(() -> "ERRORS: " + result.errors());
+    }
+
+    // This should be invalid - int32 should reject decimal values
+    assertThat(result.isValid())
+      .as("int32 should reject decimal value 3.14")
+      .isFalse();
+    assertThat(result.errors())
+      .as("Should have validation errors for decimal value")
+      .isNotEmpty();
+  }
+
+  /// Test that integer types accept valid integer representations with trailing zeros
+  /// RFC 8927 §2.2.3.1: "An integer value is a number without a fractional component"
+  /// Values like 3.0, 3.000 are valid integers despite positive scale
+  @Test  
+  public void testIntegerTypesAcceptTrailingZeros() throws Exception {
+    JsonValue schema = Json.parse("{\"type\": \"int32\"}");
+
+    // Valid integer representations with trailing zeros
+    JsonValue[] validIntegers = {
+      JsonNumber.of(new java.math.BigDecimal("3.0")),
+      JsonNumber.of(new java.math.BigDecimal("3.000")),
+      JsonNumber.of(new java.math.BigDecimal("42.00")),
+      JsonNumber.of(new java.math.BigDecimal("0.0"))
+    };
+
+    Jtd validator = new Jtd();
+
+    for (JsonValue validValue : validIntegers) {
+      Jtd.Result result = validator.validate(schema, validValue);
+
+      LOG.fine(() -> "Testing int32 with valid integer representation: " + validValue);
+
+      assertThat(result.isValid())
+        .as("int32 should accept integer representation %s", validValue)
+        .isTrue();
+      assertThat(result.errors())
+        .as("Should have no validation errors for integer representation %s", validValue)
+        .isEmpty();
+    }
+  }
+
+  /// Test that integer types reject values with actual fractional components
+  /// RFC 8927 §2.2.3.1: "An integer value is a number without a fractional component"  
+  @Test
+  public void testIntegerTypesRejectFractionalComponents() throws Exception {
+    JsonValue schema = Json.parse("{\"type\": \"int32\"}");
+
+    // Invalid values with actual fractional components
+    JsonValue[] invalidValues = {
+      JsonNumber.of(new java.math.BigDecimal("3.1")),
+      JsonNumber.of(new java.math.BigDecimal("3.0001")),
+      JsonNumber.of(new java.math.BigDecimal("3.14")),
+      JsonNumber.of(new java.math.BigDecimal("0.1"))
+    };
+
+    Jtd validator = new Jtd();
+
+    for (JsonValue invalidValue : invalidValues) {
+      Jtd.Result result = validator.validate(schema, invalidValue);
+
+      LOG.fine(() -> "Testing int32 with fractional value: " + invalidValue);
+
+      assertThat(result.isValid())
+        .as("int32 should reject fractional value %s", invalidValue)
+        .isFalse();
+      assertThat(result.errors())
+        .as("Should have validation errors for fractional value %s", invalidValue)
+        .isNotEmpty();
+    }
+  }
 }